Method of and apparatus for varying the number of phases of polyphase currents.



No. 628,358. Patented July 4, I899.

H. A. ROWLAND. METHOD OF AND APPARATUS FOR VARYING THE NUMBER OF PHASES0F PDLYPHASE OURRENTS.

(Application filed July 16, 1894.)

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S-vwewtoz un macaw No. 628,358. Patented Jul 4, I899. H. A. owman.

m-zmon or AND APPARATUS r08 VARYING THE NUMBER or PHASES 0F POLYPHASECURRENTS;

(Application fllqd July 16, 1894.)

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No. 628,358. Patented July 4. [899.

H. A. ROWLAND.

METHOD OF AND APPARATUS FOR VARYING THE NUMBER OF PHASES 0F POLYPHASECURRENTS.

(Application filed July 16, 1894.) (No Model.) 6 Sheets-Shoot 3.

No. 628 358. Patented July 4, I899. H. A. ROWLAND.

METHOD OF AND APPARATUS FOR VARYING THE NUMBER OF PHASES 0F POLYPHASECURBENTS.

Application filed .m 1a, 1894.) (Nb Model.) 6 Sheets-Sheet 4.

wvauboz (WWW 4 m: Norms vzrzns co. wonxumo, WASHINGTON. a c m No.628,358. Patented July 4, I899. H. A. ROWLAND.

METHOD OF AND APPARATUS FOR VABYING THE NUMBER OF PHASES 0F POLYPHASEGURBENTS.

(Application filed July 16, 1894.) I (No Model.) 6 Shaots-Shoet 5.

@X w'naowo No. 628,358. Patented July 4, I899; u. mnowuup.

METHOD OF AND APPARATUS'FOR VABYING THE NUMBER OF PHASES 0F POLYPHASECURRENTS.

(Lpplicatinp. filed July 16, 1894.)

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N ITED STATES PATENT OFFICE.

HENRY A. RO'WLAND, OF BALTIMORE, MARYLAND.

METHOD OF AND APPARATUS FOR VARYING THE NUMBER OF PHASES 0F POLYPHAS ECURRENTS.

SPECIFICATION forming part of Letters Patent No. 628,358, dated July 4,1899.

Application filed July 16, 1894. Serial No. 517,726. (No model.)

To all whom, it nuty concern:

Be it known that I, HENRY A. ROWLAND, a citizen of the United States,residing at Baltimore city, in the State of Maryland, have inventedcertain new and useful Improvements in Methods of and Apparatus forVarying the Number of Phases of Polyphase Currents; and I do herebydeclare the following to be a full, clear, and exact description of theinvention, such as will enable others skilled in the art to which itappertains to make and use the same.

My invention relates to methods of and apparatus for changing the numberof phases of a polyphase current and changing the polyphase current intocontinuous current.

I prefer to use in describing the number of phases of a current thefollowing system: Suppose a ring-armature to be wound with a continuouscoil and to be revolving in a twopole field. If it is tapped at threeequidistant points, three'phase current will be obtained. If at fourequidistant points, fourphase current will be obtained, and so on. It isthus evident that the expression twophase current should, strictlyspeaking, be applied only to what is ordinarily known as single-phasecurrent, while the ordinary biphase should more properly be spoken of asfour-phase.

To accomplish the transformation of currents of one system or number ofphases to currents of another system, I prefer to use alink-transformer, by which term I in this specification and in theclaims thereto attached designate a transformer having two magneticcircuits, preferably, of course, through soft iron interlinked, so thatat one point the two magnetic fluxes will flow through the same core andat other points they will be separate. I may wind both the parts of thecore common to both circuits and the parts not common with coils, soproportioned that the number of phases of the secondary cu rrent will bedifferent from the number of phases of the primary, as will behereinafter By this means I am able to change any polyphase system intoany alternating system whatever.

The use of a link-transformer is preferable to the use of a number ofmagnetically-disconnected transformers with coils wound over two cores,for the reason that the link-transformers superpose magneticfluxes andnot simply inductive effect and furnish a simple and completeentity,easily made and handled, mechanically strong, and electricallyvery simple.

\Vhen it is desired to change polyphase current into direct current, Ihave found it advisable to use a polyphase current of many phases, asthe resulting direct current is then more uniform. My system ofpolyphase transformers is particularly applicable to such work, so thatone feature of my invention resides in generatinga polyphasecurrent,trans- Initting it, transforming it into a polyphase currenthaving a greater number of phases, and then transforming it into directcurrent.

Reference is had to the accompanying drawings, wherein the same partsare indicated by the same letters and numerals throughout the severalviews.

Figure 1 represents a graphic method of determining the resultantmagnitude and phase of an electromotive force or a magnetomotive forceproduced by two currents difiering in phase and of the same or differentmagnitudes when acting in series with each other. Fig. 2 shows a methodof connecting the secondary cores of two transformers in open circuit toproduce an eight-phase from a fourphase (ordinary two -phase) current.But two coils are shown, the rest being omitted for the sake ofclearness in the diagram. Fig. 3 shows a section of the core of alink-transformer in which the links are placed together in such a mannerthat a part of the magnetic circuit of adjacent links is common to both.Fig. 4 shows a section of the core of a Wheel form of such a four-linktransformer, the spokes of which form a common part of the magneticcircuits of adjacent links. Figs. 5 to 5 show diagrammatically a varietyof forms which may be given to link-transformers, the lines representingthe elements of the magnetic circuits. Figs. 5 to 5 showthreelinktransformers. link transformers, and Figs. 5 to 5 show sixlinktransformers. Fig. 6 shows a graphic method of determining theproportions of the primary coils for a five-link transformer, in whichthree-phase current is changed to fivephase or to tenphase. Fig. 7 showsa graphic Figs. 5 to 5 show four-' method of determining the proportionsof the primary coils of a four-link transformer from which four-phase oreight-phase current may be obtained, the primary current beingfourphase. Fig. 8 shows a section of the core of a five-link transformerof the wheel form. Fig. 9 shows a graphic method of determining theproportions of the primary coils for two four-link transformers suppliedby four-phase current when it is desired that the magnetic fluxes in thetwo transformers shall differ in phase, so that eight-phase current maybe obtained from each of the transformers; but the two resultingeight-phase currents shall be dephased from each other. Fig. 10 shows agraphic method of determining the proportion of the secondary coils anda method of connecting them in order to obtain an eightphaseelectromotive force from a four-link transformer. Fig. 11 shows a methodof connecting the secondary coils of a transformer to obtain atwelve-phase electromotive force from a four-link transformer. Fig. 12shows a method of connecting the secondary coils of a transformer toobtain a sixteen-phase electromotive force from a four-link transformer.Fig. 13 shows a method of connecting the secondary coils of a four-linktransformer to obtain eight or sixteen phases. Figs. 14 and 15 show themethod of determining the ratio of thewindings of the secondary coils oneach of the two four-link transformers in order that the phases of onewill be midway between the phases produced by the other, and actingtogether they will produce a sixteen-phase electromotive force. Fig. 16shows a closed-circuit method of winding primary and secondary coils fora four-link transformer, by which Various combinations may be produced.Fig. 17 shows a method of revolving a pair of brushes synchronously overa fixed commutator. Fig. 18 shows a method of revolving a commutatorsynchronously, the brushes being fixed. Fig. 10 is a diagram ofconnections for deriving an eightphase electromotive force from anordinary two-phase current, here called a four-phase current. Fig. 20shows a closed-coil method of connecting up the secondary coils of afourlink transformer, using the spokes only to obtain an eight-phaseelectromotive force and is the same as that shown diagrammatically inFig. 10. Fig. 21 shows two transformers so connected as to generate inthe secondary coils two sets of five-phase electromotive force, suchthat the series of phases produced by each of the transformers fallsbetween those produced by the other, so as to form a single set often-phase electromotive forces.

In Fig. 1 let A B and A D represent in magnitude and phase twoelectromotive forces or two currents or two magnetomotive forces ormagnetic fluxes, in fact, any two quantities whatever whose variationsfollow the same law, the lengths of the lines representing the magnitudeof the quantities either maximum or effective 011 any convenient scale,and the angles a and [5 representing their phase differences from someother sine function A Z assumed as a standard. Then it may be provedthat A C will represent, if the two quantities be superposed,as byconnecting two electromotive forces in series, the resultant sinefunction both in magnitude and phase, on the same scale and from thesame standard of reference A Z. The magnitude of the resultant will be AO and its phase angle 7/.

In Figs. 3, 4, 8, and 16, I I are elements of the magnetic circuits of alink-transformer and K K those parts which are common to two magneticcircuits. These links may obviously be wound in a number of differentways, and the methods of determining such windings for different caseswill now be described.

Various methods of combining phases are possible. One is illustrated inFig. 2, in which E and E may be supposed to represent two coils wound ondifferent cores and excited by equal currents of the phases /3 and a,respectively. The number of turns of the secondary coil G, wound on thesame core with E, corresponds to the length of the line A D, while thenumber of turns of G, wound on the same core with E, corresponds to thelength of A B. Neglecting transformer lag, which is not important where,as in this specification, only the relative phases of secondary currentsare considered, the resultant electromotive force impressed on the wires11 H will correspond in magnitude and phase with the line A O. This isthe general principle on which the various forms of my invention arebased; but it may be applied in many different ways.

In Fig. 6, P Q, P R, and P S represent the three currents of athree-phase system. It is desircdto produce from them a five-phasesystem. Draw the pentagon, as shown, in any desired position withrelation to lines P Q, the. Then from any angle of the pentagon, as m,draw the line on 0 parallel with one of the lines of the three-phasecurrent, as P R, and from n draw at c parallel with another of thelines, as P Q. Then if 'm 0 be compounded with o n the result will be 'mat. If now any five-link transformer, as the one shown in Fig. 8, haveone of its arms wound with two coils whose number of turns isproportional to m o and n 0, respectively, and these two coils beconnected to the proper terminals of the three-phase systemthat is tosay, the ones corresponding to P R and P Qthat particular arm will bethe seat of a magnetic flux which in magnitude and phase corresponds tom n. In the same way lines may be drawn from the other angles of thepentagon and the windings for the other arms found. It is thus evidentthat the five arms-of the transformer will be the seat of five-phasemagnetic fluxes, while the rims will also be the seat of five-phasemagnetic fluxes displaced in phase, as the flux in each rim is theresultant of the fluxes in the two adjacent arms and is half-way betweenthem in phase. Secondary coils may be wound on the rims or on the armsand will take off fivephase or ten-phase current of any desired voltage.In the same way the diagram of Fig. 7 may be applied to the transformershown in Fig. 4 or to any of the transformers 5 to 5. Let P Q and P Rrepresent the two currents in what is usually known as a twopliasesystem, though I prefer to call it a four-phase,. as it is evident thatthe phase displacement is one-quarter of a circle only. Draw the squareas shown and from any two angles, as m and a, draw lines parallel to thetwo lines P Q and P B. These lines meet at 0. If now we place on one ofthe four links of the transformer two coils, one proportional to m o andone to n 0, and connect the coil proportional to m o to the primaryterminals corresponding to P Q and connect the coil proportional to 0 nto the terminals corresponding to PR, the magnetomotive force in thatparticular link will correspond to m n. In the same way the other linksmay be wound to correspond with the other three sides of the square. Theprimary coils are wound on the arms or on the rims, as preferred, andthe secondary coils may be wound on either or on both. If the primarycoils be wound, for instance, on the rims, secondary coils may be woundon both the spokes and rims and will then give an eight-phase current;but as the flux in each spoke will be the resultant of two fluxes ninetydegrees from each other it will be equal, as is obvious from geometry,to the square root of two times the flux in the rims. Therefore thesecondary coils on the rims should have a number of turns equal to thesquare root of two times the number of turns in the coils on the spokes.

The angle which any particular side of the square makes with the line PQ is notimportant, and the result is that a large number of transformersmay be wound with a different proportion in the primary coils to givethe same result. Fig. 9 shows how two such transformers may be wound togive sixteenphase current from four-phase. The diagram is the same, butthere are two squares displaced from each other by one-sixteen th of acircle. Itis thus evident that by winding two transformers like thatshown in Fig. 4 with the windings indicated by the set of lines m 0, 0 nand m 0, 0' 17., respectively, a sixteen-phase current will be obtainedin the secondaries.

Figs. 10 and 20 show the connections for a four-link transformerdesigned to give eightphase current in the secondary. The primarywindings (not shown) are supposed to be fourphase and may be wound onthe arms or on the rims, as preferred. The magnetic fluxes in the armswill be four-phase-that is to say, ninety degrees from each other-andrepresented by the sides of the square h 6 df. Inscribc in the squarethe octagon h a b, &c.,

of which every other angle coincides with one angle of the square. Drawthe'perpendiculars a i, cj, (to. Then the sides of the octagon willrepresent the eight-phase system required. Any side of the octagon, as ab, is the resultant of two perpendicular lines, as a v1 and i I). Thenif we Wind on one of the arms of the transformer of Fig. 20 the coil a11 and connect it in series with the coil ib of the next adjacent spokethe electromotive force from a to b will correspond to the side ct b ofthe octagon in Fig. 10. In the same way the other sides of the octagonare produced, and the currents taken off at a b c d e f g h areeight-phase currents.

Figs. 12 and 13 are similar and will readily be understood.

Fig. 19 shows the method of obtaining an eight-phase current from afour-phase current by the use of two simple transformers and correspondsalso with Fig. 10. E and E are the two primaries whose currents aredisplaced from each other by ninety degrees. CL 1) c, 850., are thesecondary terminals. The windings will be obvious from a comparison withthe diagram. The principle is the same as before-that is to say, each ofthe eightphase currents is the resultant of the two quartenphasecurrents taken of the proper magnitude and direction.

Figs. 14 and 15 show how the two sets of polyphase electromotive forcesA B A E and A B A E may be obtained from the fourphase electromotiveforces A O A D. It will be noted that this is accomplished in the mannerabove explained by suitably choosing the lengths of the lines A O, A D,A 0 A D 850., and that the two resulting systems are intermediate inphase.

In Fig. 16 is shown a four-link transformer wound with two closedwindings of eight coils each. With this transformer many combinationsmay be produced. If four-phase current (ordinarily two-phase) beintroduced into one set of coils on the spokes, as by the pair ofterminals 8 1, 2 3, 4 5, and 6 7, fourphase current of different voltagemay be collected from the pairs of terminals 16 9, 10 11, 12 13, and 14.15 and also from the sets of terminals 16 11, 1O 13, 12 15, and i 9,while from the whole set of terminals 9, 10, 11, 12, 13, 14, 15, and 16eight-phase currents may be taken ofi. It is therefore evident that froma linktransformer having a plurality of magnetic phases a secondarycurrent of any desired number of phases may be obtained in manyvarieties of ways.

By the well-known principle of transformers the windings above describedas secondary may be used for the primary, and vice versa.

G, Figs. 17 and 18, represents the conductors, leading from a source ofpolyphase curthe commutafor H.

N, Fig. 17, represents two metallic rings insulated from each other andfrom the supporting-shaft W and each joined by a conductor ofelectricity to one of the brushes K.

0 represents brushes rubbing on the rings N and connected to theconductors of electricity P, from which a continuous current isobtained.

Q represents two metallic rings insulated from each other and from theshaft IV and joined by conductors of electricity to the windings of thearmature T. More than two rings Q may be employed, if desired.

L represents the armature of a synchronous motor.

R represents a pair of brushes rubbing on the rings Q and joined to theconductors of electricity S, through which the current is supplied tothe armature L. The number of brushes R must correspond with the numberof rings Q, if more than two be employed.

U represents a plurality of metallic rings insulated from each other andfrom the supporting-shaft X and each joined by a conductor ofelectricity to a bar of the commutator H.

V represents metallic brushes rubbing on the rings U and joined to theconductors of electricity G.

Y represents an ordinary drum-armature or the armature of a synchronousmotor; but the same connections may be made with revolvingfield-magnets.

In order to produce a continuous current from a polyphase current, arecourse is had to the apparatus shown in Figs. 17 and 18. If in Fig. 17the conductors G are connected to a source of polyphase current and thebrushes K are caused to revolve by the armature T of a synchronousmotor, then when the armature and brushes are revolving in synchronismwith the current a continuous current can be taken off from the brushes0. Current is supplied to the armature through the brushes R and therings Q and may be derived from the original polyphase current or fromspecial coils on one of the main transformers altogether. The fieldcoils of the motor may be excited by any of the known means. In Fig. 18the brushes K are fixed and the commutator revolves with the armature,to which it is rigidlysecured. The commutator-bars are joined tothe'source of polyphase current through the rings E, brushes V, andconductors G. The armature-coils may be connected to some or all of thecommutator-bars or may be supplied through a separate set of ringsconnected either directly or through transformers to the main current.

It is evident that if the number of bars on the commutator is two,three, and four or more times the number of phases of the current thenthe armature need only revolve one-half, one-third, one-fourth, &c.',times as fast. It is also evident that both the commutator and brushesmay revolve and that a continuous current will be obtained from thebrushes K when the difference in speed is in synchronism with thecurrent.

Then the difference of speed of the two parts is not in synchronism withthe current, an alternating current of a different fre quency will beobtained.

There are so many ways of revolving the commutator or brushes insynchronism with the current that I cannot mention all. However, themethod of stationary commutators and brushes revolved by connection withthe revolving magnets and a stationary armature having alternatingcurrents conveyed to it either directly from the fixed commutator orfrom separate coils on the transformer or from a separate transformerentirely seems to me to offer the fewest moving connections. It, is alsoto be noted that transformers with only one or two limbs may be used inthe same manner as one with a greater number.

In Fig. 21, E E are two transformers, each provided with five magneticpaths, as shown,

joined together at the ends, as in the forms described above. Two phasecurrents, of phase-angles represented by the two arrows, enter and passto the coils c e and e a, respectively. The secondary coilsf f to]" ofthe transformer E are connected in a closed circuit alternately with thecorresponding coils f f to f of the transformer E so that the order ofthe coils in the closed circuit is f ff f f f f f f f f- The P y coils ee c e are so wound in accordance with the principles above explained asto produce in the magnetic circuits of E a set of fivephasemagnetomotive forces and in the magnetic circuits of E a second set offive-phase magnetomotive forces displaced by 0.1 of a period, orthirty-six degrees in time, from the magnetomotive forces of the firstset. The result is to generate in the secondary coils two sets offive-phase electromotive force such that the series of phases producedby each of the transformers falls between those produced by the other,soas to form a single set of ten-phase electromotive forces. Leads G Gpass from the connections between the various coils f f, &c., to acommutator H, on which bear brushes K K, connected, as shown, to ringsJ, and thus through brushes 0 to an external circuit. Vt ith thisarrangement by revolving the commutator at a proper speed two-phasealternating currents may be converted into continuous current, or viceversa.

In this specification and in the claims thereto annexed the action ofthe transformer-lag has been neglected, as the effect is the same forall secondary coils, and I have considered the question as if thecurrent in the secondary of an ordinary transformer were in phase withthat in its primary.

Having thus described my invention, what I claim, and desire to secureby Letters Patent of the United States, is

1. The method of changing alternating current to direct, which consistsin setting up by the alternating currents, dephased magnetomotiveforces, superposin g said magnetomotive forces, and producing therebyelectromotive forces of a number of phases greater than that of theoriginal alternating current and commutating the current resulting fromsaid magnetomotive forces, substantially as described.

2. The method of changing alternating current to direct, which consistsin setting up by means of the alternating current dephased magnetomotiveforces in a link-transformer, superposing the magnetic fluxes resultingfrom said magnetomotive forces, and commutating the current induced bysaid magnetic fluxes, substantially as described.

3. The method of changing the number of phases of alternating currents,which consists in generating dephased magneticfluxes by said alternatingcurrents, superposing said fluxes, generating thereby dephasedelectromotive forces, and taking off currents due to electromotiveforces, one or more of which is the resultant of two or more of theabove-mentioned dephased electromotive forces sub stantially asdescribed.

at. A link-transformer having a plurality of magnetic circuits, a set ofprimary coils and a set of secondary coils, some coils in one of saidsets being wound on parts of the core common to two magnetic circuitsand some 011 parts not common to them, in combination with a commutatingapparatus connected to said secondary coils, substantially as described.

5. The combination with a source of electricity, of a link-transformerhaving a plurality of magnetic circuits,conductors of electricityconnecting said source of electricity with said transformer and aplurality of primary coils wound on the parts of the core common to twomagnetic circuits, and the parts not common to them, so as to produce aplurality of-m agnetic phases, substantially as described.

6. The combination with a source of electricity of a link-transformerhaving a plurality of magnetic circuits, conductors of electricityconnecting said source of electricity with said transformer, and aplurality of primary coils wound on the parts of the core common to twoadjacent magnetic circuits so as to produce a plurality of magneticphases, and a plurality of secondary coils wound on both the parts ofthe core common to two magnetic circuits, and the parts not common tothem, and connected so as to produce a plurality of phases in thesecondary circuit, substantially as described.

7. The combination with a source of electricity of a link-transformerhaving a plurality of magnetic circuits, conductors of electricityconnecting said source of electricity with said transformer andaplurality of primary coils wound both on the parts of the core common totwo magnetic circuits and the parts not common to them, so as to producea plurality of magnetic phases, and a'plurality of secondary coils woundon the said transformer and connected so as to produce a plurality ofphases in the secondary circuit, substantially as described.

8. The combination with a source of electricity of a link-transformerhaving a plurality of magnetic circuits, conductors of electricityconnecting said source of electricity with said transformer and aplurality of primary coils wound both on the parts of the core common totwo magnetic circuits, and the parts not common to them, so as toproduce a plurality of magnetic phases, and a pluralityof secondarycoils wound both 011 the parts of the core common to two magneticcircuits, and the parts not common to them, and connected so as toproduce a plurality ofphases in the secondary circuit, substantially asdescribed.

9. The combination with a source of electricity, of a plurality oftransformers, each having a plurality of magnetic circuits, conductorsof electricity connecting said source of electricity with saidtransformers, a plurality of primary coils wound on said transformers soas to produce a plurality of magnetic phases in each, the series ofmagnetic phases produced by any one transformer falling between thoseproduced by the other, so as to form a complete cycle, substantially asdescribed.

10. The combination witha source of electricity, of a plurality oftransformers, each having a plurality of magnetic circuits, conductorsof electricity connecting said source of electricity with saidtransformers, a plurality of primary coils wound on said transformers soas to produce a plurality of magnetic phases in each, the series ofphases produced by each transformer falling between those produced bythe others, so as to form a complete cycle, and a plurality of secondarycoils wound on the magnetic circuits of said transformers, the saidsecondary coils being connected in such a manner as to produce a greaternumber of phases in the secondary current thanexists in theelectromotive force exerted on said secondary coils by the iron of saidtransformer, substantially as described.

11. The combination with a source of electricity, of a plurality oftransformers, each having a plurality of magnetic circuits, con-.ductors of electricity connecting said source of electricity with saidtransformers, a plurality of primary coils wound on said'transformer soas to produce a plurality of mag netic phases in each, the series ofphases produced by each one of the transformers falling between thoseproduced by the other, so as to form a complete cycle, and a synchronouscommutator connected to said transformer, substantially as described.

12. The combination with a source of electricity, of a plurality oftransformers, each having a plurality of magnetic circuits, conductorsof electricity connecting said source of electricity with saidtransformers, a plurality of primary coils wound on said transformer soas to produce a plurality of magnetic phases in each, the series ofphases produced. by each one of the transformers falling between thoseproduced by the other, so as to form a complete cycle, a plurality ofsecondary coils wound on the magnetic circuits of said transformers, thesaid secondary coils being connected in such a manner as to produce agreater number of phases in the 10 secondary current than exists in theelectromotive forces exerted on said secondary coils by the iron of saidtransformers, and a synchronous commutator connected to saidtransformers, substantiallyas described.

In testimony'whereof I affix my signature in presence of two witnesses.

1 HENRY A. ROXVLAND. \Vitnesses:

VERNONMASGATT, H. H. RoWLAND.

